Radio aerial



R. W. BROWN June 12, 1934.

RADIO AERIAL Filed May 20, 1931 2 Sheets-Sheet l NVENTOR RoY W. 5E0 w/v ATTORNEYS Patented June 12, 1934 UNITED STATES PATENT OFFICE RADIO AERIAL Application May 20, 1931, Serial No. 538,645

6 Claims.

This invention relates to radio aerials such as are used for transmitting radio programs from broadcasting stations, and more especially it relates to radio aerials of which the mast itself constitutes a vertical antenna or aerial for the purpose of radiating radio rays substantially parallel or tangent to the surface of the earth at the base of the mast.

Radio aerials of the character mentioned are recognized as superior to the conventional type of aerial in some respects in that the radiated energy produces strongest possible horizontal radiation while diminishing the upward or vertical radiation. The reduction of the indirect ray produces less fading of signals, and obviates to a certain extent interference with distant stations. However, such aerials as heretofore provided have had certain deficiencies of which difficulty of exact tuning, capacity to ground, and

2.0 radiation absorption due to adjacent local objects may be mentioned, and it is to the alleviation of these conditions and to the improvement of the general operation of mast aerials that this invention is directed.

The chief objects of the invention are to produce electrically exact radiations; to provide adjustability whereby electrically exact radiation may be achieved; to decrease the antennae capacity to ground; to reduce absorption due to surrounding local objects; to increase horizontal field strength for a given power input, or conversely, to obtain the same horizontal strength for less power input; to provide a radio mast embodying and adapted to achieve the foregoing objects; to provide a radio mast of safe and relatively light construction; and to eliminate the shadow or re-radiation effect of conventional radio masts. More general objects are to improve the quality of radio broadcasts; and to reduce the cost thereof.

Of the accompanying drawings,

Figure 1 is an elevation of a radio aerial embodying the invention in its preferred form, a part thereof being broken away;

Figure 1a is a reduced scale elevation of the complete radio aerial partially illustrated in Figure 1.

Figure 2 is a detail sectional view, on a larger scale, of the top portion ofthe mast;

Figure 3 is a section on the line 3-3 of Figure 2; and

Figure 4 is a detail perspective view, on a larger scale, of the supporting structure for one of the legs of the mast.

55 Referring to Figure 1 of the drawings, 10

is a mast of the open lattice type which tapers towards the top, and at the bottom is formed with four legs such as the legs 11, 11. Each of said legs rests upon and is secured to a frusto conical metal apron 12 that is mounted upon the upper ends of a plurality (herein shown as four) low capacity insulators 13, 13, the latter being of elongate cylindrical form, and substantiallj vertically disposed with their lower ends spread apart to provide lateral stability.

The lower ends of the insulators 13 are mounted in respective sockets 14, 14 that are attached to each other and to the top of a platform 15 upon which they are mounted, the platform being supported at an appreciable distance above ground upon a lattice framework 16 that rests upon and is anchored to a pier 17 of concrete or other suitable material that is sunk into the ground. The arrangement provides that the portion of the mast that is to function as an antenna, (the part above the insulators 13) is positioned a substantial fraction of a wave length (about one-tenth) above the ground.

At the top of the mast proper is a guidesleeve 20, and somewhat below the latter is a supporting plate 21 upon which is mounted a flanged collar 22. Slidably mounted in the sleeve 20 and collar 22 is a tubular extension 23 that extends a substantial distance above the sleeve 20 and has its upper end portion provided with a pair of metal cross-arms or spars 24, 24, the latter being disposed in horizontal planes, and at right angles to each other. The extension 23 is supported at a determinate elevation by a set screw 25 that is threaded through the collar 22 and through the wall of the extension, the extension being bored to receive the set screw 25 after the mast has been erected. Antenna wires 26, 26 are connected to the respective outer ends of the cross-arms 24, and descend vertically therefrom and have their lower ends connected to the corner posts of the mast, about half Way down the same, as illustrated in Figure 1a, the mast itself thereby becoming an aerial which, in an electrical sense, is substantially vertical. At the base of the mast, just above the aprons 12, the corner posts of the mast are connected to a common terminal 27 by respective conductors 28, 28, and a Zeppelin connection or feeder 29 extends from the terminal 2'7 to a transmitting building (not shown) which may be more or less distant from the mast.

The mast is designed to function as a half wave vertical radiator, and the arrangement by which the upper portion of the mast is adjustable as to height permits exact tuning of the mast. Being positioned an appreciable distance above ground upon low capacity insulators, the antenna capacity to ground is decreased and there is less absorption due to surrounding local objects, such as building, wires and trees. Antenna capacity at the top of the mast is increased by the use of the spreaders or crossarms 24. The aerial is particularly adapted to the higher frequencies above 1500 kilocycles, although structural consideration does not necessarily limit its application to the higher frequencies.

Since there is no lateral antenna pull at the top of the mast, its construction can be relatively light. The mast is provided with four legs instead of three legs as a safety factor, and the mast would not collapse through the failure of one leg.

By radiating a maximum percentage of horizontal waves that are substantially parallel to or tangent to the surface of the earth, and by reducing absorption and other power losses, it is possible to obtain greater field strength with a given power input, or the same field strength with a lesser power input, with the result that substantial reduction in the cost of broadcasting is efiected.

Modifications may be resorted to within the scope of the appended claims which are not limited wholly to the specific construction shown and described.

What is claimed is:

l. A radio transmitting aerial comprising a metal mast, cross arms at the top thereof, and antenna wires secured to the end portions of the cross arms and descending vertically therefrom and secured at their lower ends to the mast, whereby an electrically symmetrical structure is provided.

2. A radio transmitting aerial tower comprising a metal mast, cross arms at the top thereof, antenna wires descending from the ends of the cross arms and secured to the mast, and means for adjusting the elevation of the cross arms.

3. A combination as defined in claim 2 including means for insulating the mast from the ground.

4. A combination as defined in claim 2 including means for supporting the mast a substantial fraction of a wave length above the ground.

5. A radio transmitting aerial tower comprising a metal mast, an extensible section at the top of the mast, cross arms mounted upon extensible section, and vertical antenna wires secured to said cross arms and to the mast structure.

6. A half wave vertical radio radiator comprising a tuned tower having a relatively wide base and tapering to a small cross section at the top, said tower being insulated from the ground, a cross arm at the top of said tower, and parallel wires electrically connecting the cross arm and top or" the tower to the base of the tower, thus making the exterior portion of the tower electrically vertical.

ROY W. BROWN. 

